There are a variety of wheel-body forming apparatuses proposed by the prior arts including the one disclosed in the U.S. Pat. No. 3,803,890. This prior art proposes an apparatus which forms a wheel body by applying rolling process using specific constituents including four rollers which are respectively set to four positions on the external circumferential surface of a work making up the wheel body to be processed through the mandrel in the center of these rotative members to allow the objective work to be held in position in the manner of freely rotating itself while allowing the shape-forming roller to press itself against another roller before eventually forming up a complete wheel body. However, the above-cited wheel-body forming apparatus is not provided with any member corresponding to the supporting roller securely holding the mandrel. This not only causes the strength of the mandrel to lower itself when the rolling process is underway, but the apparatus itself needs to independently provide complex mechanism for stably rotating the mandrel. Furthermore, since the above-cited wheel-body forming apparatus needs to correctly regulate four positions of the external circumferential surface of the work by delicately operating four rollers, the work piece cannot fully be extended itself in the direction of the diameter, thus eventually resulting in the poor rolling efficiency, while making it difficult for the apparatus cited above to make up a work having the perfect roundness.